This circuit is more sensitive than the previous one, in the sense that we can use weaker and more distant light sources. The sensor must be mounted on an opaque tube with a lens that focuses on the distant source. Distances of up to more than 5 meters can be covered with this configuration. The adjustment is made on the 4.7 M Ω trimpot, and the relay must have a coil according to the supply voltage and a maximum current of 50 mA. The circuit is also slow-acting, producing a brief closure of the relay contacts when activated. This circuit is recommended for detecting large and slow objects. The light source can have the same characteristics as the previous circuit. The configuration is shown in the figure.
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